1. Field of the Invention
The present invention is directed to improvements in shallow depth audio loudspeakers. Accordingly, the general objects of the invention are to provide novel systems, methods, and/or apparatus such character.
2. Description of the Related Art
Permanent magnet/moving coil driven speakers have not significantly changed in over 50 years. These speakers (transducers) are based on the Lorentz Law which dictates that a conductive loop carrying current within a magnetic field creates an electromotive force from within the magnetic field. The mechanical elements of a loudspeaker depend on mechanical suspension spring constants and the corresponding losses.
The primary factor constraining the depth of a voice coil driven speaker is its suspension points. The cone surround and the spider are the two common suspension components. The surround attaches to the outer edge of a rigid cone body and is typically very compliant to accommodate the movement of the cone while stabilizing its motion. The spider is also at least partially compliant (often made of resin impregnated woven cotton, poly-cotton, or NOMEX™) and its primary function is to maintain the centering of the voice coil in the magnetic gap throughout motion of the moving assembly (cone, voice coil, spider, surround, lead wire). The spider and surround attachment points typically dictate the motional clearance of the moving assembly relative to the fixed motor/magnet assembly. This, in turn, drives the overall depth requirement.
One relatively recent development in the speaker art has been the introduction of the segmented/slotted magnetic yoke with complementary cones/spiders that may pass therethrough. Using such a structure it is possible to make speakers of a given specification that are much shallower in depth than might have been previously possible. Since low profile (shallow depth) speakers may be desirable (or even necessary) in certain applications, a number of such designs have been proposed. These include: U.S. Pat. No. 3,792,394 to Bertagni; U.S. Pat. No. 5,081,684 to House; U.S. Pat. No. 6,865,282 to Weisman; U.S. Pat. No. 8,290,199 to Pircaro; U.S. Pat. No. 4,190,746 to Harwood et al.; and U.S. Pat. No. 7,155,028 to Lin. These patents are hereby incorporated by reference in their entirety. While all of these designs have their advantages, no particular design is considered far superior to the others and additional developments/improvements remain available.